Decompress a single file from a zip folder without writing in disk

Question

Is it possible to decompress a single file from a zip folder and return the decompressed file without storing the data on the server?

I have a zip file with an unknown structure and I would like to develop a service that will serve the content of a given file on demand without decompressing the whole zip and also without writing on disk. So, if I have a zip file like this

zip_folder.zip
  |  folder1
       |  file1.txt
       |  file2.png
  |  folder 2
       |  file3.jpg
       |  file4.pdf
  |  ...

So, I would like my service to receive the name and path of the file so I could send the file.

For example, fileName could be folder1/file1.txt

 def getFileContent(fileName: String): IBinaryContent = {
    val content: IBinaryContent = getBinaryContent(...)

    val zipInputStream: ZipInputStream = new ZipInputStream(content.getInputStream)
    val outputStream: FileOutputStream = new FileOutputStream(fileName)

    var zipEntry: ZipEntry = null
    var founded: Boolean = false
    while ({
      zipEntry = zipInputStream.getNextEntry
      Option(zipEntry).isDefined && !founded
    }) {

      if (zipEntry.getName.equals(fileName)) {

        val buffer: Array[Byte] = Array.ofDim(9000) // FIXME how to get the dimension of the array
        var length = 0

        while ({
          length = zipInputStream.read(buffer)
          length != -1
        }) {
          outputStream.write(buffer, 0, length)
        }
        outputStream.close()
        founded = true
      }
    }

    zipInputStream.close()
    outputStream /* how can I return the value? */

  }

How can I do it without writing the content in the disk?

Answer 1

You can use a ByteArrayOutputStream instead of the FileOutputStream to uncompress the zip entry into memory. Then call toByteArray() on it.

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Also note that, technically, you would not even need to decompress the zip part if you can transmit it over a protocol (think: HTTP(S)) which supports the deflate encoding for its transport (which is usually the standard compression used in Zip files).